The present invention relates to a method and apparatus for attaching metal members for assembling automotive vehicle structures.
It is known that the manufacture of automotive vehicles often requires that metal members be attached to each other for forming automotive vehicle structures. Friction stir welding is one potential method of attaching metal members. Conventional friction stir welding typically requires a rotating tool to be translated along an interface between surfaces of metal members for softening or melting portions of the members at the interface. In turn, the softened or melted portions intermix and harden to form metallurgical bonds between the members. During a conventional friction stir welding process, however, substantial amounts of liquidized material may be lost or unused forming weaker bonds. Moreover, a conventional stir welding process may require relatively large amounts of time for forming metallurgical bonds. Thus, there is a need for improved techniques, fasteners or both, alternative to conventional friction stir welding for achieving high integrity attachment of a metal members.
The present invention meets these needs by providing an improved method for attaching metal members, with particular utility in the formation of components for an automotive vehicle. The method includes the steps of providing a first metal member and contacting the first metal member with a second metal member. A substantially cylindrical rotatable member is provided with a central axis and an axially extending passage, wherein the member is formed of a material with a melting point and hardness higher than that of the first and second metal members. The rotatable member is rotated while frictionally engaging it with the first metal member for locally heating and melting a portion of the first metal member, and penetrating the rotatable member through the first metal member. The rotatable member is also rotated while frictionally engaging it with the second metal member for locally heating and melting a portion of the second metal member. A wire is fed through the axially extending passage and melted as it exits the axially extending passage. The resulting molten wire is mixed with the resulting molten metal of the first and second member, and solidified to form a joint.